ABSTRACT
When a drug is ingested, it may reach its peak concentration in the system gradually but then starts to decay quickly, or may reach the peak quickly and starts decaying slowly. Half-life is the time taken to go from the peak concentration to half that concentration. Figure H.1 shows the half-life for a drug that reaches its peak gradually but decays quickly. Half-life is utilized to measure the duration that a drug remains in the system and may form the basis for prescribing the periodicity (once a day, twice a day, etc.) of intake. For example, Schulze-Bonhage and Hintz [1] suggested that the antiepileptic drug perampanel can be prescribed once daily because of its long half-life.
